The infectious hypodermal and hematopoietic necrosis virus (IHHNV) belongs to the family Parvoviridae and causes reduced and irregular growth with cuticular deformities of the rostrum and the previous appendices of white shrimp (Litopenaeus vannamei ). Although no high mortality is reported, it produces 10-50% growth reduction, causing a reduced weight and lower market prices. Three pathogenic and two nonpathogenic genotypes of IHHNV (lineage 1-3 and types A-B, respectively) have been described. The presence of IHHNV was diagnosed for the first time in Costa Rica in 2016 in a farm using molecular techniques; however, the genotype was not determined. The objective of the present study was to determine the presence and genotypes of IHHNV present in farms cultivating L. vannamei in Costa Rica.
A cross-sectional descriptive study was carried out in 15 shrimp farms distributed in the northern Pacific region. Between 2017 and 2018, water samples, postlarvae and juvenile shrimp were collected during a production cycle. The samples were subjected to DNA extraction and analyzed by the polymerase chain reaction (PCR) technique, using different protocols and primers to determine the genotypes of IHHNV present in our country. On the day the juvenile shrimp were collected, a survey was applied to the producers to know about the handling conditions. The physical-chemical parameters of the pond water were measured this day . The information obtained through the surveys and the PCR results were processed using the SAS statistical program to determine risk factors. The presence of IHHNV was established in 86.6% (13/15) of the farms and in all types of samples analyzed (water, postlarvae, stomachs and hepatopancreas of juvenile shrimp ). S equencing of the amplified products determined the presence of IHHNV lineage 3 in all positive samples, showing a 99.2-100.0% identity with a sequence isolated from a shrimp in Venezuela (KM485615.1), with variation s in only 1-3 nucleotides.
Risk factors were not determined due to the large number of positive farms. Poor management practices, especially non optimal physical-chemical parameters of the water and use of antibiotics without regulation was determined in most of the shrimp farms. We conclude, that non- optimal physical-chemical parameters and the presence of pathogenic strains of IHHNV could be causing the low productivity in these farms . We recommend conducting studies to assess the economic losses that IHHNV and non-optimal physical-chemical parameters of the water is causing in these farms, and to control the use of antibiotics in the ponds.